----- The ISOGG article says:
"One review, published in April 2004 paper by Professor Kenneth Anderson,
University of Oklahoma, reviewed and studied 66 published studies on the per
cent
of non-paternal events in father-son tests.....

The non-paternity rates for the 3 groups were 1.9%, 3.9%, and 30.9%. Fathers
with high paternity confidence seem to be correct in assessing
non-paternity, the
1.9% rate. “High and unknown” levels of paternity confidence exhibited the
3.9% rate. Those who didn’t know, e.g., low paternity confidence, had the
highest non-paternity rate, n.b. 30.9%.

For the purposes of this discussion I have concluded that the 3.9%, rounded
to 4% per generation is at least representative of what we could expect. All
non-paternal rates are highly idiosyncratic, depending on location, time,
religion and other factors. But remember that a 4% non-paternality rate
could be
made up of about 2% illegitimacy and 2% other causes. "

---------- A.J. Levin wrote:

Is this an "NPE rate" or an aggregate NPE/bad-genealogy rate?

I suspect the latter based on the number of false and absurd trees I have
seen. Your rate is nearly three times higher than the median number that the
classic peer-reviewed article on the subject found: